Telephone system



April 9, 1940.

R. E. oLLls E-r AL.

TELEPHONE SYS TEM Filed June 17, 1938 2 Sheets-Sheet 1 llxl. nouw w BN u @Uk 9255 k .okt .QQ

Af 1 9, 1940. R. E. coLLls Er A1. `2.196.250

TELEPHONE sars'rlm Filed June 17, 193B 2 Sheets-Sheet 2 mi E K WMV IL Imam wow Si wumo.

RECOLLS u INVENTORS RQEZHERSEY Arr Nar Patented Apr. 9, 1940 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM e Raymond E. Collis, Summit, Ralph E. Hersey, Madison, N. J., and James B. Newsom, Great Neck, N. Y., assignors to Bell Telephone Laboratories, Incorporated, New York, poration of New York N. Y., a cor- Applcation June 17, 1938, Serial No. 214,352'

8 Claims.

conversational connections to assess charges against the subscribers who initiate the calls.

The circuit for operating a subscribers message o register in these automatic systems usually extends fnder that serves to extend the calling line to the selector switches and controlling equipment. After passing through the contacts of the line switch or nder, the operating circuit is then'connected by way of suitable cross-connecting frames to the message register individual to the subscribers line. v

An object of the present invention is to increase the reliability of systems ofthe foregoing character and to obtain a greater assurance of the `registration of all calls rmade by the subscribers.

A feature of the invention is a system in which connections are established by means of automatic switches under the control of a common controlling mechanism or marker, and in which the marker makes a test at a certain stage in the progress of establishing a connection to determine whether the operating circuit for the register of the calling line is intact and in proper condition for the subsequent operation of the register. If the message register circuit is found to be intact, the marker proceeds in the regular manner with the further establishment of the connection, and at some subsequent time the operating current is applied to the message register circuit to operate the register and assess the call. However, if the marker is not satisfied with the test of the register operating circuit, it refuses to proceed with the establishment of the connection.-

Failing to obtain his connection, the calling subscriber may consult an operator who will order the troublefman to investigate and remedy the cause of the trouble.

Another feature of the invention is a system having 'some lines equipped with message registers and also having lines of other classes, and in which' the marker receives a class-of-service indication Whenever a call is made by a line other than a message rate line and ,from'this informafrom common f controlling equipmentr through the contacts of the line switch or linev tion knows thatv the message register test should' be omitted. Having this information, the marker omits the test that it' would otherwise make and proceeds to establish the connection for the calling line the same as itv would had it made a satisfactory test in case a message rate line were calling.

` A furtherfeature of the inventionl is a system of the character above described in which service to any message rate subscribers line may be denied him by opening the operating circuit of his message register. When any subscriber attempts s to make a call after the message register circuit of his line has been opened to deny him service, the marker in making its usual test nds that the register circuit is open and refuses to set up the connectionfor him. The subscriber, on making inquiry of the operator, will learn why he has been unsuccessful in obtaining the telephone connection.

v.These and other features of the invention will be described more fully in detail in the following specification and will also be set forth in the accompanying claims. In the drawings accompanying the detailed specication, Figs. l and 2 taken together illustrate, partly inrdetail and partly in diagram, the equipment of a central oice system embodying the features of the present invention.

Fig. 1 shows subscribers lines of different classes appearing in the line link switches of the central oiice and also illustrates the district selector switches and a central oilice sender for controllingv them, together `with other controlling and connecting equipment; and

Fig. 2 illustrates an oice selector switch for extending the calling lines to outgoing trunks and a marker which cooperates with the central oilice sender to control the operation ofthe district and oice-switches,

'I'he invention is disclosed in an automaticr telephone system in which automatic switches of the cross-bar typeare used as the medium for eX- tending connections from subscribers lines overV trunks to other subscribers lines. These crossbar switching mechanisms are controlled by regis'- ter senders at the central oiice, which receive the designations from the calling subscribers dials, and by decoder markers, which are connectable to the senders 'for receiving information from the senders, and. which are also connectable to the proper switch frames for' the purpose of testing the outgoing trunks and for testing the connecting links and for operating the magnets of switches to establish the contems, and since it is not necessary to an understanding of the invention that the system in all of its details be disclosed, much of the circuits and equipment has been eliminated in the present disclosure for the sake of simplicity. And in the following descriptions reference will be made to numerous operations which are not fully disclosed in allv of their details. Wherever such references occur it will be understood that the circuits and equipment so referred to are already old in the prior art, and in particular reference is here made to the following for a detailed disclosure of all operations and equipment referred to herein but not specically disclosed: Carpenter Patent 2,093,117 of September 14. 1937; and Carpenter application Serial No. 214,356, filed JuruJ 17. 1938.

The subscribers lines appear in the contacts of primary line link switches. For example, the two-party message rate line and the nonmessage rate line |36 appear in the contacts of the primary switch |06. The primary switches are connected by links to secondary line link switches, such as the secondary switch |09, and these secondary switches in turn have access to district trunk or junctor circuits extending to the primary district cross-bar switches, such as the primary switch |22. The primary district switches in turn have access through links to secondary district switches, such as the secondary switch |25. The secondary district selectors are connected by links to the primary oice selectors. the primary oflice selectors having access in turn to secondary office selectors which in turn have access to the outgoing trunks, such as the trunk 2M. Two of the oice selectors, primary switch 204 and secondary switch 201, are illustrated.

The district junctors have access through crossbar sender link switches to common register senders. For example, the district junctor |15 and other similar junctors have access through primary and secondary link switches |28 and |29 to any one of a number of common register senders, such as the sender |30. The register sender |30 is connectable to an idle one of the controlling markers, such as the marker illustrated in the lower part of Fig. 2, through sender connectors |16. The markers are connectable to the frames of district and office switches by means of frame connectors. One of the district frame connectors |17 is' illustrated. This frame connector serves to connect the marker shown in Fig. 2 and other markers to the district frame including the primary and secondary district selectors |22?v and. |25. Similar frame connectors, not shown in detail herein, are providedV for connectingr the markers to the oice frames.

When a message rate subscriber on the twoparty line |35 or a non-message rate subscriber on line |36 removes his receiver from the switchhook to initiate a call, he will be automatically connected through the primary and secondary line link cross-bar switches to a district junctor circuit. Said district junctor then makes connection with an idle originating subscriber sender |30 via primary and secondary cross-bar switches |28 and |29. Usually five pairs of primary crossbar switches and five secondary switches are employed to gain access to a common group of senders. When an idle sender is connected. a dial tone is given to the subscriber and he proceeds to operate his dial, such as the dial |0| or the dial |03, in accordance with the number of the party he is calling. When the sender completes registering the oiice code portion of the wanted subscribers number, it seizes an idle decoder marker, such as shown in Fig. 2, out of the common group, through the sender connector |16. Said decoder marker then functions to receive the code from the sender and translates the same for setting up certain conditions in the sender according to the nature of the terminating central ofiice. Another function of the marker is to select an idle trunk and an idle path to it from the district junctor and to operate selecting and holding magnets in the district link and ofce link frames to close the path through to the trunk. If the marker cannot nd idle elements to form a continuous connection from the district junctor to the idle trunk which is selected, it attempts to select an idle trunk on the mate ofce frame and then attempts to rind an available channel to it from the district junctor. Each trunk group is divided into two subgroups which appear respectively in the cnice switches of a pair of mate frames. If the marker fails to nd an idle trunk or an idle channel thereto, it notifies the sender which then chooses another marker. The second marker goes through the same operations except that a trunk in an alternate route is sought. If there is no alternate route it searches again among the trunks of the original route. If the second marker trial is unsuccessful, a third marker is seized which directly establishes connection with an overflow circuit. When a connection is established through the district and ofce switches, the marker is released and the sender proceeds to complete the connection to the calledv station or to an operator who will connect to the called station.

A detailed description will now be given of the particular features of this invention. Assuming the decoder marker of Fig. 2 has just been seized by the sender as above mentioned and has been connected to the proper district frame, the operation of multi-contact marker connector relay |32 at contact |31 closes ground to lead 24.8, which may further be traced through top outer contact of relay 22| and through bottom contact of relay 228 to battery through winding of relay 22?. rI'he latter relay thereupon operates and locks through its front contacts and the break contacts on relays 222 and 223 to ground at Contact 249 von relay 23|. Relay 23| may be assumed to have operated just after the sender connector relays |33 and |34 v)first connected the sender to the marker. Marker connector relay |32 also closes a circuit for connecting the district link through to the district junctor circuit, which path may be traced from ground over lead |38 through the contacts of certain relays in the decoder indicated at |39, thence through top outer contacts of sender connector relays |34 and |33 for operating a relay in the sender. This same ground is extended through the .sender link via contacts |40 and IM, thence over lead |42 and through the winding of relay H9 of the districtA junctor to battery. The operation of the latter relay extends f het 295.

its operating path. overflead`r F43: to"bat'tfelftvA` |23 asy previously traced. Relay 218 thusv oper-- through district link primary switch connector relay i3! which operates and' likewise extendsy the operatingA ground over lead |44', contact on marker connector relay |32, lead24`, top breakv operated,"andincluding the operated relay in-v the sender above mentioned.

The decoder marker having been seized', nowy receives, from the sender, information on the code portion of the number as dialed bythe subscribed and Aproceeds to'test for an idle trunkand an idle channel through the district and oiice frames to such` trunk. When a channel is selected, relays 222 and 223 operate each over a path traced from ground at contact 250 on relay 23E through its own bottom winding. Said path for relay 222 may further be tracedthrough bottom outer contact of relay 22|, tcp outer armature and contact of relay 2|, through other marker relay contacts indicated at 253, top inner contacty oil relay 2|?, lead 2M, thence through contacts on marker connector relays |32 and `|3| to battery through the primary holding magnet |22 of the district link. Similarly the path for relay 223 may be further traced through top outer contact of relay 228 and vthrough other marker relay contacts indicated at 254, thence to battery through the secondary holding switch magnet llili on' the oiiice link frame. The priinary district and office secondary switch holding magnets operate in the circuits above traced as well as relays 222 'and 223, assuming of course, said channel is idle. The latter relays, however, openY holding circuit for relay 221' as previously mentioned, causing said relay to release and at Contact 25| to close'a path for operating the district link secondary holding switch magnet |26 and oiiice link primary switch mag- Said path may be traced from ground at contact 252 on operated relay 22|, thence through normal contacts in parallel vonkrelays 2|8 and 228 to le'ad 255, contact 25| on relay 221 and through other marker relay contacts` indicated at 255, top outer contact on relay 2|1, lea

22|, thence through a contact on connector relay |32 and junctor'relays indicated at |45 to battery through holding magnet |26 and over lead 259 to battery through holding switch magnet 205. The operating ground for magnets |26` and 225 is thereupon extended over leads |46 and 252 to the windings of the primary district and secondary ofce switch magnets respectively.' thereby Ishunting out the ground throughthe bottom windings of relays 222l and 223 to these same magnets as previously traced, causing reays and' 222 to release. The release of relay 222 with relay 22T released, thus closes a circuit for operating relay 'M8 traiced froml battery through winding of Said relay, top outer break contact of relay 22?, normal contact of relay 222,

contact 222 on relay 221, thence through armature and front or back contact of relay 2|6, contacts on relay 2|3, contacts andbottom armatureof relay through other contacts on marker relays indicated at 263, lead 202, thence through contacts on connector relays |32 and |3| to lead |42 which is now connected through a contact on operated relay ||9 to lead |52,"and then to ground at' the winding of holding magnet ates to indicate that the sleeve lead |52 is prop erly connected. Similarly the release of relay 223 with relay 227 released closes a circuit for operating relay 223 traced from battery through winding of said relay, bottom outer Contact of relay 22'?, normal' contact of relay 223, contact 258 on relay 221, thence through vother marker relayfcontacts indicated at 265 to the sleeve 251 oi? the`v outgoing trunk which is nowv grounded through' the operation oi holding magnet 206 previously described. Relay228 thus operates to indicate that the trunk sleeve is properly connected. With relays 2|8 and 228 operated therehy removing direct ground through contact 252 from leadv 255,r all holding magnets will be held ope1'atecl"'through contact 25| on relay 227 to ground 'through top winding of relay 238, thereby operating the latter relay. Relays 2|8. andV 228 also connect direct ground to the windings of relays 222' and 222 respectively to maintain the latter in' a lnon-operated position.

yWhen relay 22T released as above described it also closed a circuit' from battery through the windings of relay 22|! over contact 244 on relay 22T, lead 245, Contact |22 on' marker connector relay |32, thence through contact |29 on primary switch connector relay |3|, resistance |20, contact'lii on operated relay M9, lead |5l, thence through contact |52 orv |54 on relay l |4 over lead 15d-l on |56 through secondary and primary line link switch contacts,` terminals |51 or |58 on message register connecting rack |59, to ground through' party line message register |94 or |05'. The register, 'of course, does not operate under this test condition but the operation of relay 228i at its top Contact opens the path to ground onlead' 24| previously traced, said path being ...ie last one of three paths that have been holdingrelay 22l operated. A second path for holding' the latter relay operated was opened at the bottom-contact when relay 2|8 operated as previously described, and a third path for holding relay 22| operated was opened when relay 232 operated as previously described.

It will be understood in connection with tracing the' 'above path of message registers |134 and |85 that relay i4 may or may not be operated dependingon whether relays 2|4 and 2|'3 in the markerl of Fig. 2 have operated. The originating subscriber sender |32 makes a two-party test of the calling subecribers line before sending dial toneto the calling station, records this information, and at the completion of the dialing of the office code transmits it to the marker circuit. If, for example, the message rate subscriber at station |12, the nat rate subscriber |22, or an operator, is calling, then the sender conveys this information to the marker by withholding a ground connection from the lead |81'. If the message rate subscriber at station |19 is calling, the `sendery grounds lead |51 traced thence through the connector relay contacts over' entends the circuit of relay H4 to the top inner' armature of relay 2|3 of the marker over a path traced from battery through the Winding of said relay, bottom inner contact of relay |8, contacts |69 and |10 on connector relays |3| and |32 respectively, and lead 26|. Assuming subscriber at station |19 is calling, relay 2|3 Would then be operated so that the circuit of relay ||4 as just traced may further be traced to ground at contact 2d@ on relay 221 which is Still operated at this time. Relay H4 once operated, locks to ground through other relay contacts in the district junctor circuit indicated at thereby remaining operated for the duration of the connection so that subscriber at station |19 will be charged for the call when completed.

Referring to the test of the message register circuit above described, if this circuit is intact, relay 220 of the decoder marker circuit will operate and the marker will start releasing due to the closure of a circuit for relay 234 traced from battery through winding of said relay, thence through the contacts of a number of other marker relays indicated at 266 and contact on relay 231 which operated when the secondary oillce link holding magnet 206 operated. The circuit through winding of relay 234 is further traced through contact 261 on relay 22| which is now released, normal contact on relay 238, thence through contact 268 on relay 22| to ground through contacts on other marker relays indicated at 242. The operation of relay 234 then locks under the control of numerous operated relays (not shown) which must release before relay 234 can release. Relay 234 also removes ground which has been holding relays 23| and 233 operated. These and other relays open the cnice and district link start leads and also remove the off-normal battery and ground from the numerous relays that were operated and locked during the marker stage, and these relays release. The last one of them to release nally opens the locking circuit for relay 234. The marker is thus dismissed and from this point on the originating sender directs the setting up of the connection. When the sender has completed its function, it operates relay ||5 by connecting ground to lead |60 which may be traced through contacts on sender link frames |29 and |28, lead |6| thence through bottom armature and back contact of relay ||9 to battery through winding of relay ||5. The latter relay thus extends the talking conductors |62 and |63 via the impedance-condenser transmission bridge |64 to the trunk conductors |65 and |66 leading toward the called subscribers station.

When conversation is over and the subscriber releases, the message register |04 or |05, depending on which party made the call, is operated by the application of current to conductor |80, the circuit extending through contacts of relays ||1 and .H9 to conductor |5|.

If the relay 220 in the marker fails to operate due to the subscribers message register lead being open for any reason, relay 22| will not release following the operation of relay 238. That is, locking ground through relay contacts indicated at 242 of the marker continues to hold relay 22| operated over a path traced through contacts 239 and 270 to lead 24|, thence through the too normal contact on relay 22D and through Winding of relay 22| to battery. Since relay 22| does not release, it will be obvious that primary switch connector relay |3|, district junctor relay H9, and the operated relay of the sender abovementioned, likewise do not release following the operationv of relay 238 previously described. Thus, a path is closed for operating relay 224 traced from battery through its winding and bottom outer contact of relay 220, left front contact and armature of relay 238, contacts 269 and 239 on operated relay 22|, thence to ground through other decoder marker relay contacts indicated at 242. Relay 224 then locks to ground through contacts on operated relays 225, 230, 235 and 236 and normal contact of relay 233. Relay 224 at its bottom front contact connects ground, traced through other decoder marker relay contacts indicated at 21|, through an armature and normal contact on relay 226 to battery through slow operate relay 229 which starts the decoder marker releasing in the usual manner. While the latter relay is operating, said ground path as just traced is also connected from this point, through contacts of relay 214 of the decoder marker to lead 213, thence through contacts |12 and |13 on marker connector relays |32 and 53| to the front contact |14 on operated relay H9, thence over lead |6|, through primary and secondary sender link switches |28 and |29, and lead |60 to the subscribers sender |30 as a trouble release indication to the sender. Relay 224 at its top contact also opens the holding path for relay 2H thereby releasing the district and holding magnets so that these will be released and prevent setting up the connection.

The failure of relay 220 to operate thus results in causing the decoder to fail in setting up the connection and gives the lsender a trouble release signal. As described in the above-noted Carpenter application Serial No. 214,356, led June 1'7, 1938, the sender will make three trials in an attempt to set up the call and on the third trial, if the register circuit is still open, the contacts of relay 214 in the series circuit will be operated which prevents the operating ground for relay 229 from being connected to lead 213. The sender under this condition does not receive a trouble release signal. The relay 234 is operated and the decoder marker restores to normal and lthe sender proceeds to cut the district through and release itself, even though the decoder did not set up the district and oilice cross-points to a trunk, such as trunk 244. This then will result in the subscriber not being connected to whatever line he is calling but instead the district merely being held from his line with the sender and decoder released. When the subscriber calls the trouble condition to the attention of the operator, the trouble-man will correct it and restore the service to the subscribers line. If, however, the message register lead had been opened at the cross-connecting rack |59 by the telephone company in order to deny service to that subscriber he will be so informed.

When an operator or a subscriber of some other class, such as the subscriber of the iiat rate line |36, originates a call, the sender when seized by the sender link will register the class of service of the calling line as Well as the district frame through which the call is coming. Then when an idle decoder marker is connected to the sender, this information will be passed along to said marker as recorded in the sender, all in the usual manner as described in the above-noted Carpenter application Serial No. 214.356. led June 1'7, 1938. This and other information is recorded in the decoder marker by the operation of certain other relays called class-of-service relays. One of these class relays, relay 245, is illustrated. Therefore, on operator class calls and on lines .subscribers line having an individual message register, tan operating circuit for lsaid message Y not equipped'llwith messageregistersQsuch as 'fiat rate andcoin lines, class relay I24,5 wil'ljbe operated. Class relay 245 causes the operation of test relay 220 in a circuit from ground through the contact-of relayfMdterminal 2li), through the winding of relay 220 to battery. From this point on the marker willi be dismissed and the originating sender` will direct the setting,` up of the connection just as above described when a` message rate rline was found toibo intact.

In the foregoing description it: has beentassumed that the message ,ratef-iine illustrated is a two-party line. It isnobviou's, however, that similar service may be given to single party rnessage rate lines. of message register lines, the marker obtains ra class-of-service indication lfrom the sender and utilizes thisl information for the purpose kci inalcing a test of the message register circuit at the propel' .timein the process of setting up the ,coril hectic-n. This testfhassthe purpose or" determining whether or not the message register circuit, over which the subscribers message register' is operated to charge him for the call, is intact and is in proper operating condition. Since the marker will normally perform this test as apart of its regular functiony in establislfr'ng a connection unless it is otherwise prevented from doing so, means is provided, as fully described hereinabove, for notifying the marker whenever Y it is called upon to set up a connection from a calling line that is not equipped with a message register. In this way the marker is able to omit the test of the message register circuit and toy Jhaving a' message register individual'to said line,

an operating circuit for said message register, automatic switches, switch controlling markers for controlling the selective operation of said switches to extend the connections fromA said subscribers line, means for taking one oi markers into use in response to a call by v line, means in said marker for making atest oi' the subscribers line to determine whether saidA message register operating circuit is intact, and

means effective in case the marker isnot satisfied by said 'est for preventing the further extension of the calling line.

2. In a telephone system, a subscribers line having an individual message register, an operating circuit for said message register, automatic switches, a common switch controlling mechanism for controlling the selective operation of said switches to extend a connection from said subscrihers line, means in said controlling mechanism for making a test to determine whether the operating circuit of said register is in an i' open or a closed condition, and means effective in case the test indicates the operating circuit to be in open condition for preventing the operation or" said automatic switches tcextend the calling line.'

3. The combination in a telephone system of a On all such calls by subscribers saidI said' register, automatic switches, a common switch controlling marker, means, in said marker vfor -malsing -a test of the operating `circuit of the [message register of a 'calling subscribersline,

ineens under the control. of said marker for causing. .the selective operation of said :switches toextend the calling line in case vthe testfby said marker fmds vthe message registeroperating cir-y cuit to 'be in standard condition, and means in" said marker to prevent the operation of said automatic switches to extend the `calling line in vcase. the test by said marker nds the-message register operating circuit to be in-an unstandardr condition. y u

e. In a telephonevsystem, a subscribers line of themessage rate class, a message register individual to said line, a second .subscribers line of another class, an operating circuit iorsaid message register, automatic switches,.. a switchcorntrollingr marker for controlling the selective operation of said switches to extend connections from said f subscribers lines, means responsive to a call by the subscriber of the message rate line for caus- .ing the marker' to make a test of the operating circuitoi the individual message register, means under the control of saidl marker and dependent on the result of said test for controlling the selective operation of said switches to extend the calling message rate line, and means responsive to the initiation of a call on said second-mentioned line for causing said marker to omit said test and to control the selective operation of said automatic switchesl to extend a connection vfrom said second-mentioned line., v

5. In a telephone system, a subscribers line of the message rate class, an individual message register for said line, an operating circuit for said message register, a second subscribers line of a different class, automatic switches, a common switch controlling marker, means responsive to a call on either of said lines i'or taking said marker in use, means in the marker effectivev/hen a call is made on the message rate line forltesting the operating circuit of the individual message' register to determine whether said circuit is in a standard condition, and means effected if the test by said marker is satisfactory for causing the marker to control thelselective operation of said switches to extend the calling message rateline,

'classindicating means vresponsive to a call on said second-mentioned line for establishingin the marker an indication ci the class of the calling line, and means in said marker responsive to said class indicating means for simulating a satisfactory test of a message register operating circuit when said second line maltese,4 call to .allow said marker to control said automatic switches to extend said second-mentioned calling line. l' l 6. The combination in a telephone'system of a subscribers line having an individual message register, an operatingcircuit for said register,

4automatic switches, a plurality of markers, each arranged'to make a deiinite number oi successive trials to' establish a connection. through said switches, means in each vmarker for making a test to determine whether' said message register operating circuit is effective ,and means effective in case the marker is not satisfied with said tes-t and depending upon which trial is being made for causing a new trial to'be made with an idle one of said markersto establish the connection.

`-7. The comblnationin a telephone system of a subscribers line having an individual message register, an operating circuit for said register, automatic switches, a plurality of markers for controlling said switches, each arranged tovmake a limited number of trials to establish a given connection through said switches, means in each marker for testing the subscribers line to determine Whether said message register operating circuit is in working condition, means in each marker effective to cause a new trial by an idle one of said markers provided the marker is not satised with the test of the subscribers line and the limited number of trials have not been made, and means in each marker operative when the marker is engaged in the iinal trial for preventing the establishment of the connection through said switches in case the marker is not satisfied with the test of the subscribers line.

8. In a telephone system, a subscribers line of the message-rate class, a message register individual to said line, a subscribers line of another cla-ss, an operating circuit for said message register, automatic switches, register senders and markers for controlling the selective operation of said switches to extend connections from said lines, means for taking one of said senders and one of said markers into use in response to a call by either one of said lines, means in the marker controlled by the sender for establishing a class indication identifying the class of the calling line, means in the marker for making a- 

